Coating method and apparatus for plastic tubing and the like



Jan. 27, 1953 Filed April 29, 1950 0. c. STAHL 2,626,426 COATING METHOD AND APPARATUS FOR PLASTIC TUBING AND THE LIKE A 3 Sheets-Sheet 1 0.90412 CI STA/IL,

JZ/vs/vroR.

.Hi/EB/Vk, BEEHLEQ, PV/QQEL,

HEez/c; and CALDWELL, Arraelvsys- Jan; 1953 o. c. STAHL COATING METHOD AND APPARATUS FOR PLASTIC TUBING AND THE LIKE Filed April 29, 1950 3 Sheets-Sheet 2 Osa e C. STAHL Jkvszvroie.

By Arroeysys.

Jan. 27, 1953 o. c. STAHL 2,626,426

COATING MET D AND APPARATUS FOR PLASTIC me AND was LIKE 3 Sheets-Shee 3 Filed April 29, 1950 Jkvewrae.

Wbeeez BEEHLEP,

.H'ez/a and CALDWELL, By

Arroeusvs.

Patented Jan. 27, 1953 COATING METHOD AND APPARATUS FOR PLASTIC TUBING AND THE LIKE Oscar C. Stahl, Los Angeles, Calif., assignor to American Extruded Products 00., Inc., Hollywood, Calif., a corporation of California Application April 29, 1950, Serial No. 158,956

12 Claims, 1

This invention relates to coating apparatus for automatically and continuously coating a hose,

as of a vinyl plastic type, with a smooth and uniform layer of material or paint-like substance, the preferable ingredients and nature of which is more specifically set forth in the copending application of applicant and Elbert Davis, Serial No. 90,667. For purposes of convenience of nomenclature the words paint, coating or layer" will be employed although it will be understood that any appropriate coating material is intended and that reference to preferred forms of such coating and the ingredients thereof will be had to said copending application.

It is intended by the instant invention to provide, alone or in combination with an extrusion device, an apparatus which will convey a continuous plastic extrusion or the like through a painting or coating device without distortion, with uniform application of pressure and tension thereto, assisted preferably by gravitational forces and by uniformly operating conveying means.

It is likewise intended to provide new and improved means and methods for coating vinyl plastic tubing to finish and cure the same, together with said coating. 6

In view of the above considerations, among others, this invention has among its objects the provision of new and improved apparatus of the desired character described for obtaining a superior coating and total product.

It is also among the objects of the invention to provide a new and improved hose-conveying apparatus for the purpose intended. Likewise among the objects of the invention is the provision of a new and improved painting method.

A further object of the invention is the provision of new and improved painting means.

Another further object of the invention is the provision of improved non-tensioning means whereby more uniform products are obtained and a more nearly circular cross-section is achieved for the tubing or hose during the coating operation and/or thereafter.

Yet another object of the invention is the provision, alone and in combination with other desired apparatus and means, of new and improved methods and specific apparatus for achieving an improved and continuous coating and curing process.

This invention also contemplates among its objects provision of improvements over prior art methods and apparatus heretofore intended to accomplish generally similar purposes, including 2 provision of new and improved preliminary tensioning, stretching and cooling means and methods by which a truly round tube is obtained.

Other and more specific objects and advantages will appear and'be brought out more fully in the following specification considered with reference to the accompanying drawings throughout which like parts are designated by like numerals.

In the drawings- Figure 1 is an elevational view of a preferred form of coating apparatus embodying this invention;v

Figure 2 is an enlarged sectional view taken as on a line 2-2 of Figure l, parts'being cut away;

Figure 3 is a further enlarged detailed sectional view taken as on a line 3-3 of Figure 2;

Figure 4 is a horizontal sectional view taken as on a line 44 of Figure 2;

Figure 5 is a plan sectional view taken as on a line 5-5 of Figure 2;

Figure 6 is a view similar to Figure 3 and illustrating a modified form of coating element embodying this invention.

Referring more particularly to the drawings, there is shown by way of example, but not of limitation, a frame structure generally designated by the numeral 20 andcomprising vertical and horizontal bars having adjustable sleeves, 22 thereon, said sleeves being slit longitudinally and being clampingly associated with the bars as by means of screws or the like 23. By this construc tion, a delicate balance and desired inter-relationship of the other parts to be described may be readily maintained or compensated for, withal providing a readily adjustable and transportable construction capable of ready assembly or disassembly.

' Any conventional continuous extruder or the like 25 is positioned adjacent the frame 20 in a position such that any extruded tubing or the like 26 is carr iedas over a glide 21 and through a cooling bath28, in a trough 29, under uniform tension and as guided and supported by rollers 30 or the like.

Thence the tubing 26 is drawn by a gear In the initial forming of the tube, the extruding die is preferably made oversize relative to the desired ultimate diameter of the tubing. The rim speeds, therefore, of the wheel 35 and hence its associated wheels 30, 31, 32 and 33, is greater than the lineal speed of extrusion of the tubing from the extruder 2 5.

As a practical matter 'such speed differential is like the diameter of the extrusion relative to the ultimate desired diameter of the tubing, not ordinarily over 25%.

Thereby the tubing in its more fluid orplastic state is drawn out and elongated; the resultant tension serving to pull and hold the tubingto a desired true circular cross section.

In such conditionof initial tension, the tubing is directed from the extruder into the cooling bath 28 wherein the temperature of the tubing is brought down to control and stop the elongation and to fix the tubing in its rounded cqndition, of tension.

Thereafter the tubing should be conveyed without-distortion or undue stress; accordingly during curingv hereinafter mentioned, the curing temperature will not be such as to render the tubing again plastic to an extent which would disturb-its round shape.

-ther wheels 38, 39. and- 40 are commonly driven (as by gear and sprocket means not shown) at a uniform rim speed-so that. their circumferential peripheries in engaging the tubing-Z6 at spaced stations therealong acts upon said tubing with a minimum of distortion, tension and/or friction.

By means of the illustrated. and described arrangement-"a portion 42' of the tubing 26 ismoved upwardly overthe wheel 39.,all' wheels or pulleys engaging the tubing 26 being appropriately rounded and grooved in a complementary mannor to they desired curvature ofthe tubing.

After passing over the wheel '39, the tubing is passed vertically downwardly through a pot 45R and. battery of curing lamps or other elements 46. The descending portion 4T|= of the tubing 26; isfthen passed horizontally around the driven wheel 40, thence through a second cooling bath 48' contained as in a trough 49 whence the tubing is conveyed toward the left as illustrated 'in- Figure-l to a place of storage or use.

It will be noted thatthever-ticallydescending portion- 41; ofthe' tubing is-longerthan the ascending portion 42. Thus, in addition to the nontensi'o'ned conveying of the tubing on the wheels aforesaid, the weight of the descending portion- 41 tends, without outside power, to move the tubing gravitationally in the desired downward direction through the coating pot 45' and the curing elements 46.

The truly round, substantially relaxed tubing retains acondition of desired optimum. unstressed fullness in its descent through the pct 45.

Suchpot 45- is' preferablyadju'stably mounted as upon a support 50. adapted. to telescope as within a frame member 5|, the latter being capable or angular adjustment in jahorizontal plane asby means of. 'a.sleeve 52' clampable. upon a supporting frame member 53;

An annulus 54 may supportirods or the like 55" to which. cooling fins 5.6. are. optionallysecured in vertical spaced relationship.

retaining ring. 58-.- issupported .as by 'means of bolts-.59.. upon the base. Stand-preferably includes radially directed-'setescrewsipositioned in.

circumferential spaced relationship for centering an annulus 6| within which an internally tapered painting nipple 62 is disposed.

Said painting nipple 62 is accurately centered about the descending tubing portion 41' anddepending upon the viscosity of the paint 64 and upon the thickness of the ultimate coating desired upon the tubing -26--may maintain a clearance, of, for example, to 9 of an inch over the tubing diameter.

The base 65 of the nipple preferably includes a flange 66 adapted to nest Within 3. correspondingly shaped recess 61 formed in the annulus 6|, and 'seats accurately thereagainst, preferably floatingly without the forced axial confinement thereof by the bottom 68 of the pot, the latter being preferably bolted as by screws 69 to the annulus 61. A desired more or less free-floating action of the nipple 62 is thereby achieved and the centering of the tube and nipple is assisted by the painting action of the tapered bore 10 through which the descending portion 41 of the tubing passes.

It will be noted that by the present construction, sufiicient distance being retained between the uppermost wheel 39 and the nipple 6-2,'the tubing portion 51 is free to move slightly laterally to any required extent necessary to retain a centered position within the nipple.v This centering tendency is insured by the fact that any slight movement of the tubing. to one or an other side of the. nipple bore tends to foster an. increased flow of the paint on thefiopposite' side of the bore betweenthe' bore wall'and the tubing, thereby causing a decreased. lateral pressure at right angles toincreased-fiow coup;- teracting any 'such sidewise movement of the: tubing through the bore.

Thus, a combination of. forces cooperate in such manner that when-the descending. tubing portion 41 passes through tliepaint and pot, a metered and uniform peripheral coatingwhose thickness may readily be adjusted by the size-ofthe bore in. the nipple and by the viscosity of the paint is obtained as aforesaid;

The nipples illustrated in Figures lthrough 3 can be made of any rigid material such as plastic, wood, metal or the like.-

It has been found. mar nate-satisfactory nipple 80, or only the-tips-thereof;.maybe'made; as illustratedin Figure. 6, from a; resilientniate= rial such as rubbensaid tin-81 of which-retainsa normal sliding contact with. the-descending tubing portion 41; inieffeca. brushingo'r'wipii'ig the-same with a. coating-of. the paintiwhi'ch', as-

in the previous embodiment, initially i'sQheldin the top of the tapered bore 82 from whence it is drawn by adhesion, cohesion. or other wetting of the tube 41 downwardly into and past the tip 8|.

Just as the thickness of the desired applica'-- tion may be varied and adjusted by increasing the diameter of the tip relative. to that otthetubingin the first embodiment: underidisct1ssien, so the thickness of the coating-iofthe-modifiedtip-form of Figure 6 may beadjustedz'by. such factors and also theresilience. or degree of= con-' strictionof the nipple clip 81 about the tie-=- scending tube.

As stated heretofore, both: form of .nipple' are retained in a sufficiently large opening at= the bottom of the potthat facile removal 'and/or re placement ofthe nipple maybe; accomplished.

In lieu of: rigid material or-resilient'materiah the-'- tip 8|: may, if desired,'-.be=formedi.of bristlesy cloth, or any other appropriate matted or fibrous substance. It has been found preferable however to utilize a rigid type of substance as herein specified on the one hand (Figures 1-3) or resilient form (Figure 6) on the other.

'Now referring to the curing apparatus 46 the same may comprise a plurality of heating elements I mounted in circumferential spaced relationship between upper and lower complementary C-frames [0| hingedly secured together at their ends upon pintles I02. One or both of the opposite ends of the C-frames may be secured as on a frame I04, and projecting fingers I95 engageable as against a stop I06 on the frame member assure proper centered positioning of the- C-frames about the descending tubing portion 41. 3

The length of the heating element and its intensity related to the speed of travel of the tubingtherethrough' will control the curing time. Such curing will be governed by the nature of the material ofwhich the tube is formed and also by the nature of the coating material employed in accordance with said copending application.

After passing through the tubes and being heated and cured, and when the tubing has passed through a cooling bath 48 the cycle of continuous manufacturing process of the tubing per se is substantially complete.

This invention features provision of a new and improved means and apparatus for continuously coating and curing plastic tubing or the like in a referred, eflicient, economical and uniform method resulting in the tubing of maximum smoothness, roundness and uniformity in its outermost layers. It features likewise the provision of new and improved painting meansand methods and moreover, but without limitation, new and improved heating procedures and techniques as well as apparatus. A new efficiency and naturalness of product as well as process results. Economy is achieved, manufacturing simplified, and desired uniformity, and therefore superiority of the resultant product is attained. The manner of passing the tubing through the paint results in distortion and tension of the tube even without the added assistance of the tapered orifice itself.

Although I have herein shown and described my invention in what I have conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of my invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent structures and methods.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A tubing manufacturing apparatus including: means for continuously forming a plastic tubing; conveyor means adjacent said forming means, said conveyor means including pulley means for lowering said tubing gravitationally in a vertical path to convey said tubing vert cally to a level different from that at which said forming means is disposed; coating means disposed below said pulley means on said vert1cal path for receiving and coating said tubing during its gravitationally induced movement along said vertical path; and means for setting a coating on said tubing disposed immediately below said coating means and along said vertical path.

2. A tubing manufacturing apparatus including: means for continuously forming a plastic tubing; conveyor means adjacent said forming means, said conveyor means including pulley means, means for driving at least the first and last of said pulley means at uniform rim speed, at least two of said pulley means being arranged in a vertical relationship to lift said tubing upwardly, the last of said pulley means being arranged below the uppermost of the lifting pulley means with its axis of rotation spaced outwardly from the axis of rotation of the uppermost lifting pulley means a distance equal to the sum of the radii of the uppermost and last pulley means so that the tubing will follow a vertical path between the uppermost lifting pulley means and the last pulley means; coating means for applying a coating to said tubing positioned between said uppermost lifting pulley means and said last pulley means and disposed adjacent said uppermost pulley means; and setting means for setting a coating on said tubing disposed along said vertical path having its uppermost end adjacent the underside of said coating means and its lowermost end adjacent the last of said pulley means.

3. A tubing manufacturing apparatus including: means for continuously forming a plastic tubing; conveyor means adjacent said forming means, said conveyor means including a plurality of pulley means and means for driving the first and last of said pulley means at uniform rim speed, at least two of said pulley means being arranged in a vertical relationship to lift said tubing upwardly, said lifting pulley means including the first of said pulley means, and at least two of said pulley means being arranged to permit the gravitational descent of said tubing, the lowermost of the pulley means permitting said gravitational descent being the last of said pulley means; coating means disposed between the uppermost of the lifting pulley means and the last of said pulley means for coating said tubing; and setting means disposed between said coating means and the last of said pulley means for setting the coating on said tubing.

4. A tubing manufacturing apparatus including: means for continuously forming a plastic tubing; conveyor means adjacent said forming means, said conveyor means including a plurality of pulley means and means for driving the first and last of said pulley means at uniform rim speed, at least two of said pulley means being arranged in a vertical relationship to lift said tubing upwardly, said lifting pulley means including the first of said pulley means, and at least two of said pulley means being arranged to permit the gravitational descent of said tubing, the lowermost of the pulley means permitting said gravitational descent being the last of said pulley means; coating means disposed between the uppermost of the lifting pulley means and the last of said pulley means for coating said tubing, said coating means including a not containing a fluid coating material therein, said pot having an opening at its top for the axial reception of said tubing and a nipple slidably engageable with the external periphery of said tubing for coating the same; and setting means disposed between said coating means and the last of said pulley means for setting the coating on said tubing.

5. A tubing manufacturing apparatus including: means for continuously forming a plastic tubing; conveyor means positioned adjacent said forming means, said conveyor means includin pulley meanspsaid pulley means including first and last commonlydriven pulleymean's disposed below and at opposite sides of-an uppermost intermediate free-wheeling pulley-means, said tubing being lifted between said first and uppermost pulley means and gravitationally lowered between said uppermost and last pulley'means; coating means for coating said tubing disposed adjacent said uppermost pulley means; and setting means disposed'immediately below said coating means'forsetting said'coating on-said tubing.

6. An apparatus=as characterized in claimpl, said continuous forming means'includingistretch ing and cooling means 'for said tubing.

7. An apparatus aspharacterized in claim 1, said continuous forming means 'includingstretching and cooling means for :said 'tubingprsaid stretching means comprising a pulley adjacent the forming 'means carrying said tubing and having arim speed less than 25% of the forming speed of said forming means.

' 8. A method of coating a vinyl plastic tubing or the like comprising'thesteps of continuously extruding said tubing, continuously stretching and thereby elongating said tubing so extruded to round the same while the same is still plastic from its extrusion, passing said tubing vertically downwardly into and through a body 'of fluid coating material gravitationally, continuously wiping said coating, setting said coating 'material on the tubing, curingsaid coating, and cooling the tubing and coating so cured;

9. A method of coating a vinyl plastic tubing or the like comprising the steps'of continuously extruding said tubing, continuously stretching and thereby elongating said tubing so extruded to round the same *while the same i still-plastic from its extrusion, "fixing-the tubing'while so stretched and'rounded, passing said tubing vertically downwardly into and through'a body-of fluid coating .material gravitationally; continuously wiping saidcoating, setting said coating material on'the tubing, curing said coating, a d cooling the tubing and coating-so cured.

10. A method of coating a vinyl plastic tubing or the like comprising the steps of continuously extruding said tubing, continuously stretching not more than 25% and thereby elongating-said tubing so extrudedsto round. the.:sam'eawvhi1e;ti1e' same-is stilluplasticrtronnits extrusion, fixing the tubing while so "stretchediand :rounded, passing said tubing :vertically rdownwarldly :into .and through a body-of fluid :coating material gravitationally, continuously wiping said i coating, setting said coating material on thettubingzcurin said coating, and cooling :the' tubingand coating so cured; 1

11. A method of .coatmg a'vinylplastic tubing or'the'like comprising 'fthefsteps-of passing said tubing vertically downwardly I solely under :a gravity inducedi tension and --applying a vinyl plastic material havingrlistinctly difierentzcharacteristics from'the' material of said tubinetto said tubing at-a station along its downward rd'escent completely ,therearound, curing-said coating, and cooling the'tubingand coating sozcured.

12. A method or coating a" vinyl mla'stic tubing or the like comprising the steps-of: conveying said tubing upwardly solely mnder a gravity induced tension, passing said tubingwerticallydownwardly into and through a body of vinykplastic-material having distinctly fiifierent charaoterls'tics from the material of said tubing, gradually' rw strictingthe diametric'al dimensions of said coating material inthe directionof downward travel of said tubing until said 'diametrical dimensions approximate "the des'ired coating of *s'aid tubing, passing the coated 'mubin'g continuously through a curingstation, and cooling the tiibing 'and-cdating so cured;

:RE ERENcEsbrrnn 'The followingjre'fer'ences 'are'ofrecord'in the UNITED TATEScBAI'ENT 

